Instruments which test generator sets are known in the art. As is also known in the art, such instruments evaluate generator set performance by analyzing prescribed output signals indicative of generator set output characteristics such as output voltage, frequency, current and power quality while the generator set is under a variety of electrical load conditions. An example of an instrument which tests generator sets is disclosed by U.S. Pat. No. 5,144,232, incorporated herein by reference. Disclosed therein is a device which measures the operating speed and voltage output of a generator set, thereby allowing a user to verify if the generator set operates properly. The device includes an analog AC volt meter and a digital frequency display which respectively provide a visual reading of generator set voltage and frequency. U.S. Pat. No. 5,144,232 is exemplary of known generator set testing systems, which systems comprise instruments for recording prescribed generator set outputs, such as voltmeters, ammeters, oscilloscopes and strip charts. Each such instrument is capable of recording a single prescribed output at a time.
Generator sets which are to be sold to certain military entities must comply with the test procedures set forth in MIL-STD-705C, "Military Standard, generator sets, Engine Driven, Method of Tests and Instructions", incorporated herein by reference. MIL-STD-705C explains, establishes and standardizes specific methods for measurements associated with the evaluation of generator sets. Those who sell generator sets to purchasers who require compliance with MIL-STD-705C are contractually obligated to assure that generator sets conform to MIL-STD-705C requirements. Before the purchaser accepts a batch, or lot, of generator sets, each generator set in the lot is subjected to MIL-STD-705C specified tests. A generator set which fails to meet any of a number of prescribed requirements during any test is considered defective, causing rejection of the entire lot. Furthermore, rejection is grounds for the purchaser to refuse further acceptance of generator sets from the seller until the seller implements purchaser-approved corrective action at the seller's expense.
In light of the above, those who sell generator sets invest significant resources in testing generator sets for compliance with MIL-STD-705C. In conventional generator set testing systems, a technician configures a generator set and test equipment in accordance with the requirements for a test. The test equipment generally includes a device known in the art as a load bank. A load bank imposes a prescribed electrical load upon a generator set to which the load bank is coupled. The characteristics of the load which is imposed upon the generator set is determined in accordance with load bank controls such as toggle switches and mechanical dials which are coupled to the load bank and operated by a technician.
The technician conducts the test on the generator set and records the test results by observing outputs of devices which measure test specific parameters such as generator set voltage, frequency, current and power. To conduct a test and to record test results typically requires forty eight hours. A trained analyst analyzes the recorded test results in accordance with prescribed analysis criteria, thus determining whether the generator set has passed the test. The test results typically require twenty hours to analyze.
A drawback of known generator set testing systems is that it requires several hours to conduct a single test and analyze the test results. It would be advantageous to have a generator set testing system which can automatically conduct tests and quickly analyze test results. It would be especially advantageous to have a generator set testing system which automatically conducts tests in accordance with MIL-STD-705C.
Another drawback of known generator set testing systems lies in the large amount of time spent by the technician and the analyst. The technician must continually record test data as the test is in process, and therefore cannot perform more than a single test at a time. Similarly, an analyst can analyze the results of only a single test at a time, The technician and analyst thereby act as a bottleneck in testing generator sets and analyzing test results. Furthermore, since the analyst can analyze the results of only a single test at a time, the technician must decide whether to await the outcome of the analysis before initiating another test or to immediately initiate another test. If the technician immediately initiates another test, he risks wasting valuable time and resources testing a generator set which the analysis will show to be defective. On the other hand, if the technician awaits the outcome of the analysis before initiating another test, he tests generator sets much more slowly, seriously reducing generator set testing throughput. It would be advantageous to have a system for testing generator sets in which several generator sets are tested simultaneously by a single individual.
Still another drawback of known generator set testing systems is that they depend on highly trained technicians to conduct the tests and to record test results. Similarly, such generator set testing systems require trained analysts to analyze test results. It would be advantageous to have a system for testing generator sets which does not require a highly trained technician nor a highly trained analyst.
Another drawback of known generator set testing systems is that the trained technician who records test results often introduces errors into the recorded test results by rounding a test result to an integer value or even by incorrectly transcribing a test result. It would be advantageous to have a system for testing generator sets which accurately records test results.
Another drawback of known generator set testing systems is that they do not automate the administration of the procedures set forth in MIL-STD-705C. Known generator set testing systems must be tailored to implement the MIL-STD-705C procedures. It would be advantageous to have a system for testing generator sets which automates the procedures set forth in MIL-STD-705C.
A generator set has output, characteristics, such as voltage and frequency, which generally depend on a load imposed upon the generator set. Ideally, the generator set voltage and generator set frequency remain at substantially constant values. Typically, the voltage and frequency do not remain constant, but slightly deviate from a mean voltage value and a mean frequency value, respectively. Minor deviations of the voltage from a mean voltage value, that is, deviations wherein the voltage lies within a desirable voltage range, or band, are deemed to be acceptable voltage values. Similarly, minor deviations of the frequency from a mean frequency value, that is, deviations wherein the frequency lies within a desirable frequency range, or band, are deemed to be acceptable frequency values. Unfortunately, a frequency value or a voltage value of a generator set may continually and periodically fluctuate outside of the desirable range. The periodic fluctuation of a generator set output characteristic outside of a desirable range is known as a "hunting condition", and generally indicates a generator set which does not meet specifications. In known generator set testing systems, a technician or other individual detects a hunting condition by listening to sounds emitted by the generator set. The technician, based on his experience, ascertains whether a hunting condition exists if the sounds emitted are repetitive tones of prescribed frequencies. It would be advantageous to have a system for testing generator sets which automatically detects hunting conditions.